My current network consists mostly of WIFI devices connecting to a NetGear WNDR3700 WIFI Router connected to a SAT modem. My setup runs quite nicely with Gargoyle open source firmware on Router however the restriction feature is currently broken in Gargoyle. My main workstation is a Linux Mint 18.3 connected directly to router (But also has WIFI card).

I am wondering if I can use my main Linux PC also as a ROUTER but unsure how to proceed.
Just obtaining a HIGH level view of how to accomplished this and if its worth the effort. At the end of the day I simply want to block access to certain websites (Trackers) to all my network devices. Merry Christmas and thank you the open source community.

Rather than making a general-purpose machine perform router functions, I chose to build a dedicated machine for the purpose. For the OS, I chose pfSense* https://www.pfsense.org/. This is a prefered choice not only because it places the overhead on a dedicated machine but because community maintained, distro-based features are very sophisticated and address many difficult to discover misconfigurations out-of-the-box. They are easy to setup and configure. You can block ban bad sites, ads, countries, and any custom list of domian names or IPs.

You don't need a super fancy computer for home use. I started with a VM then did my first prototype native install on a toaster I got at the dump. I now have two production pfsense builds in service, one of which serves a network of 70+ machines - effortlessly.

* There are many distros that perform this special function. I tried several before I settled on pfsense, which is a FreeBSD fork.

I actually sprang for the book "Mastering pfSense'" by David Zientara. But... the site documentation is good too.

There is a package manager built into the pfSense web interface that has several usefull addons. The esentials are suricata for intrusion detection and pfBlocker, which is the secret to controlling trafic by IPs and domains.